God wants ultimate happiness for all people and he wills only what is for their good. But the world is no longer as God made it. We inherit from our first parents a wounded nature and a broken world. The Church teaches that "God permitted such painful upheavals as the angels' fall and man's sin only as occasions and means for displaying all the power of his arm and the whole measure of the love he wanted to give the world" (CCC 760).
Great love involves great sacrifice, and the greater the personal sacrifice the greater the love and the greater the glory that follows. In the life, death and resurrection of Jesus we find a much better answer to the problem of suffering than any text book or argument can give. Jesus was born in order to lead us into the full and final life of God, but first he had to redeem us from enslavement to evil. So his life’s work became one of suffering, sorrow and rejection. He confronted the depths of human evil and yet he died with words of forgiveness on his lips. He now offers himself to the Father for ever as the price which had to be paid for our everlasting freedom.
God the Father accepts his Son’s sacrifice of love for all humanity as an apology for all the sins of the world. This powerful offering of redeeming love is constantly renewed and applied to us in our individual needs every time Mass is celebrated. We can bring our own sufferings to Jesus there and make them part of his own great sacrifice for the salvation of the world. We should do whatever we can to alleviate the sufferings of others, but Jesus also invites us to "take up our cross" each day and follow him by making our lives a sacrifice of love to God's glory and in the service of others.